The present disclosure is directed to a method of separating production from a producing well, and in particular, a well which produces oil and water from a subterranean producing formation. In the production of oil wells, it is not uncommon to obtain a mix of flowing products. One type of product obtained from the flowing well may include gas which separates as the production fluids are received at the surface. Another product that may be carried along in the production stream may be particles of the formation i.e. sand particles. The present disclosure is not concerned with either of these although they may be present. Generally, both natural gas and sand are separated in ways which are believed to be well known when the production stream is received at the surface. It is more common to encounter the production of oil and water which are mixed together. There is a generalization that oil and water will not mix, rather, they form separate phases. Even when they are produced in the form of emulsified droplets, there is a tendency for them to separate. That is not always however the case. In some instances, the water in the formation may be heavily laden with various organic salts, some of which are significantly water soluble. A "salt" is any compound formed when the hydrogen (H.sup.+) of an acid is replaced by a metal (such as Na.sup.+, Mg.sup.+, Cu.sup.+, etc.) or its equivalent (NH.sub.4.sup.+, etc). The petroleum produced by the well may contain carboxylic acid and other acids. When the hydrogen atom is replaced with a metal atom, it is no longer an "acid", but rather a "salt". This is a problem in separation, and it is equally a problem in discarding the water produced from the well, typically salty water. These organic salts include any metal salt of a low molecular weight organic acid, and a wide range of these salts can be readily detected in the production. One factor which enters into this is the range of variation in the oil/water ratio. If the amount of water is quite small i.e. one part per ten parts, or even one part per one hundred parts, then the said production stream is quite valuable. However, there are many wells which produce perhaps one barrel of oil for ten barrels of water, and other wells have been completed which have an even more undesirable ratio of oil to water. In any context, the separation of the oil and water poses a problem to the extent that there are water soluble organics mixed in the production stream. This is exemplified by several examples given herein, but a generalized statement of the problem relates primarily to typical metal salts of low molecular weight which form low molecular weight organic acids. Typically, the acid has a lipophilic tail which involves C.sub.4 and larger molecules typically up to about C.sub.18. The lipophilic tail can be straight chained, branched or cyclic. As a generalization, the formula is represented as R--COOH hence the acid form. It is not uncommon for a substantial mix ranging all the way from C.sub.4 up to about C.sub.18 to be in the stream of production. The metals that are involved can vary widely and typically include such things as Potassium, Sodium, Calcium and other salt forming metals so common to brine produced from oil and gas wells.
Accordingly, the present disclosure is directed to a solution for this problem which deviates from the idealized form of phase separated oil and water in a production stream. Departing from the idealized form, there are the water soluble organic compounds which, if not otherwise separated, will stay in the separated water. There are limits to this. Salt water disposal is always a problem, and it is particularly undesirable to dispose of salt water which includes an excessive amount of organics in the salt water. Pollution standards that presently prevail in the Gulf of Mexico forbid the discharge from a production platform of recovered salt water where the organics measure in excess of 48 ppm; occasional increases to 72 ppm are permitted for a limited interval, but the normal discharge must be 48 ppm or less. The present disclosure sets forth a method for accomplishing this.
This disclosure represents an advance over the procedure set forth in U.S. Pat. Re No. 29,908. That discloses an oil waste recovery procedure involving demulsification with flocculation. It is not concerned with removing water soluble organics from the production stream. U.S. Pat. No. 3,687,845 is directed to the removal of oil from an oil/water emulsion by the addition of a water soluble anionic polymer of relatively high molecular weight. Even so, water soluble organics are not impacted by this treatment process. A micro organism approach is set forth in U.S. Pat. No. 4,035,289. U.S. Pat. No. 4,401,570 sets forth a method for removing organic esters from a waste water stream using an acid approach which still does not provide for sufficient oil removal from the produced water stream. U.S. Pat. Nos. 4,818,410 and also 4,839,054 set forth the use of strong acids. These procedures lead to corrosion difficulties, and have an inefficient response.
The present disclosure is primarily a method which comprises the intimate mixing or commingling of an additive to the production fluids prior to separation into separate oil and water streams. The addition utilizes a strong acid, selected acids include HCl, H.sub.2 SO.sub.4, H.sub.3 PO.sub.4, H.sub.3 PO.sub.3, and citric acid, or mixtures of the foregoing acids. This will be denoted as a strong acid which lowers the pH of the produced water to 6.0 or below, the preferred range being about 2.0 to about 6.0. Of the group of acids mentioned, phosphorous acid appears to be the preferred of the several strong acids mentioned. The acid is mixed with any of a number of low molecular weight amines or amine quaternaries. It has been found that something on the order of about 5% to about 30% of the amine or amine quaternaries with the acid provides a satisfactory mixture of the acid and amine or amine quaternaries.